The present invention relates to a power-operated sword saw.
More particularly, it relates to a power-operated sword saw with two parallel and reciprocating saw blades having front saw blade tips and opposite clamping ends coupled by clamping means to a drive and provided at one side with saw teeth and at an opposite rear side guided in a guiding groove of a plate-shaped sword.
Sword saws of the above mentioned general type are known in the art. One of such sword saws is disclosed for example in the European patent document EP 267 312. At the clamping ends the saw blades of this sword saw are provided with a throughgoing opening. This opening is associated with a threaded opening of a driving base body mounted at the drive sight. The clamping end is held between the base body and a pressing member and tightened by a screw extending through these parts. In the above described construction a saw blade exchange is possible only by releasing the screw with an auxiliary tool, for example a screw driver or an inner hexagon tool. This is very inconvenient since through a lateral open housing slot the substantially different positions of the screw must be found by the auxiliary tool with relatively great time to be spent. Dust and chips can penetrate through the housing slot for mounting the saw blades and affect the operation of the saw. Each saw blade must be individually removed and mounted from the respective side of the saw housing.
The screws and the pressing member clamp the clamping end so that it rotates together with the drive. Therefore, undesired torques can be transmitted through the screws to the saw blades and reduce the efficiency of the force transmission. Due to mounting errors or due to vibrations during the operation of the saw, the screws and the pressing member can be loosened, released and lost. If the clamping ends of the saw blades are loosened during the operation of the sword saw, there is a substantial danger of injuries for the operator or the danger of damages to the saw and the workpiece, since no securing means are provided from a loosening or uncontrolled movements of the saw blades.